Cyanido‐Bearing Cobalt(II/III) Metalloligands – Synthesis, Crystal Structure, and Magnetic Properties

Abstract

AbstractNew examples of cyanido‐bearing cobalt(III/II) complexes have been obtained by treatment of CoCl2·6H2O with bidentate nitrogen donors and potassium cyanide in a methanol/water mixture. Depending on the chelating ligand, the cobalt(III) complexes PPh4[Co(en)(CN)4] (1, en = ethylenediamine), PPh4[Co(ampy)(CN)4]·1.5H2O [2, ampy = 2‐(aminomethyl)pyridine], and PPh4[Co(phen)(CN)4]·CH3OH·0.25H2O (3, phen = 1,10‐phenanthroline) and the cobalt(II) complex PPh4[Co(dmphen)(CN)3]·3H2O (4, dmphen = 2,9‐dimethyl‐1,10‐phenanthroline) were obtained. The complexes were characterized by single‐crystal X‐ray diffraction and variable‐temperature magnetic measurements. They are all mononuclear species with six‐coordinate cobalt(III) (1–3) and five‐coordinate cobalt(II) centers (4), and two nitrogen atoms from each bidentate ligand (1–4) and four (1–3) or three cyanide carbon atoms (4) build somewhat distorted octahedral (1–3) or square‐pyramidal (4) surroundings. Complexes 1–3 are diamagnetic cobalt(III) compounds, whereas 4 is a low‐spin cobalt(II) complex that exhibits Curie behavior in the temperature range 10–300 K. The g values of the X‐band electron paramagnetic resonance (EPR) spectrum of 4 both in the solid state and in dichloromethane solution at 4.0 K (g⟂ = 2.28 > g∥ = 2.0) reveal that its unpaired electron is defined by a d‐type orbital. Complexes 1–4 can be viewed as new metalloligands for metal assemblies.